The invention relates to a method and an apparatus for determining a position of a transmitter in three dimensions. Such position determination is required, for example, for an access and operation authorization system which is referred to by the expression a xe2x80x9chands freexe2x80x9d system.
In xe2x80x9chands freexe2x80x9d access authorization systems, the access authorization of a person who is requesting access is checked without the person having to carry out any action intended just to initiate the check, that is to say, for example, the insertion of a key in a lock, the pressing of an operating button on a radio transmitter, or the swiping a magnetic strip card through a card reader. xe2x80x9cHands freexe2x80x9d access authorization systems generally have an identification unit which checks the access authorization and allows access, and an identification transmitter which identifies those carrying it as being authorized for access. For access authorization monitoring, an identification unit transmits a request signal to the identification transmitter. Reception of the request signal in the identification transmitter triggers a response signal, which is in turn received by the identification unit and is compared with an expected response signal. If they match, the identification unit then allows access by the person carrying the identification transmitter.
In addition to checking the content of the response signal transmitted by the identification transmitter, it is also important in xe2x80x9chands freexe2x80x9d access authorization systems to be able to determine, in three dimensions, the position of the identification transmitter which is responding to the request signal from the identification unit. This is done in order to ensure that access authorization is given only when the person carrying the identification transmitter is located in a predetermined three-dimensional area with respect to the identification unit. To this end, in the prior art, the request signal is transmitted by the identification unit such that the identification transmitter can receive it only in this predetermined three-dimensional area. If the identification transmitter then responds to the request signal, then this is assessed by the identification unit as being a sufficient indication that the person carrying the identification transmitter is located in the predetermined three-dimensional area. However, this position determination method requires a complex, and thus expensive, transmitter in the identification unit, in order to ensure that the request signal is transmitted only into the predetermined three-dimensional area. Precise delineation of the desired three-dimensional area is, however, also possible only to a limited extent and with a high level of complexity in terms of transmission technology.
It is accordingly an object of the invention to provide a method and an apparatus for determining a position of a transmitter in three dimensions that overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, which allows accurate position determination in a simple and reliable manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, a position determining method, which includes:
transmitting a signal via a transmitter;
receiving the signal in four receivers, the receivers disposed separated from one another in three dimensions and not all in a same plane;
determining time intervals between a reception of the signal by each of the four receivers using an evaluation unit;
determining a signal delay time between the four receivers individually and the evaluation unit; and
using the evaluation unit for determining a position of the transmitter in three dimensions using the time intervals, a placement of the four receivers, and a propagation speed of the signal in space.
According to the invention, in order to determine the position of a transmitter in three dimensions, the signal:transmitted by the transmitter is received by four receivers which are separated from one another in three dimensions and are not all disposed in the same plane. In which case the time intervals between the reception of the signal by the four receivers is used to determine the position of the transmitter taking into account the positional configuration of the receivers and the propagation speed of the signal in space. High-precision transmitter position determination can thus be carried out according to the invention. Furthermore, the position determination can be carried out using the simple receivers that, according to one preferred embodiment, are antennas. The detection and evaluation of the delay time differences of the signal on reception by the individual receivers furthermore require only evaluation logic constructed from a few components.
According to a preferred embodiment, the signal transmitted by the transmitter for position determination contains a defined intensity change, which is used by an evaluation unit for position determination as a trigger in order to determine the delay time differences between the signals received by the individual receivers. This makes it easier to determine the delay time differences, thus simplifying the technical complexity in the evaluation unit.
When the position-determination technique according to the invention is used in a xe2x80x9chands freexe2x80x9d access and operation authorization system, in which the transmitter whose position is intended to be determined corresponds to an identification transmitter, it is furthermore advantageous for the transmitter which is additionally required in the evaluation unit to use one of the receivers to transmit the request signal. If an electromagnetic signal is used for position determination, it is furthermore possible to configure the transmitter and receiver as simple antennas, which can each transmit and receive an isotropic signal.
In accordance with an added feature of the invention, there is the step of transmitting a sound signal as the signal transmitted by the transmitter.
In accordance with an additional feature of the invention, there is the step of determining the position of the transmitter a plurality of times.
In accordance with another feature of the invention, there is the step of decoding and evaluating the signal from at least one of the receivers.
With the foregoing and other objects in view there is further provided, in accordance with the invention, an apparatus for determining a position of a transmitter, including:
four receivers disposed separated from one another in three dimensions and not all in a same plane for receiving a signal transmitted by the transmitter; and
an evaluation unit connected to the four receivers for determining time intervals between a reception of the signal by each of the four receivers and for determining a signal delay time between the receivers individually and the evaluation unit, and using the time intervals, a configuration of the receivers, and a propagation speed of the signal in space for determining the position of the transmitter in three dimensions.
In accordance with an added feature of the invention, the evaluation unit has an additional transmitter used to transmit a request signal to the transmitter whose position is intended to be determined, in order to trigger the signal transmitted by the transmitter.
In accordance with an additional feature of the invention, the receivers are antennas, and the additional transmitter for transmitting the request signal uses one of the antennas.
In accordance with a concomitant feature of the invention, the evaluation unit has a first device for decoding the signal received by at least one of the receivers resulting in a decoded signal, and a second device connected to the first device for evaluating a content of the decoded signal.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and an apparatus for determining a position of a transmitter in three dimensions, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.